Device Controllers
Operating systems do not deal with devices directly. Rather there is a mechanical and
electronic portion. Electronic portion is a device controller. A printed circuit card.
Look at Silbershatz Fig 13.1. Also a network interface card.
Example: CRT controller takes care of details of rescanning the CRT beam

Polled I/O
No interrupts used. CPU puts request in controller's registers and then polls waiting for
the request to nish.
Also called programmed I/O.
Might be used for debugging in operating system interrupt handler because it doesn't block.

Direct Memory Access (DMA)
What about large amounts of data to transfer? For example, disk read. Controller gets the
data and bu ers it.
CPU could only get data in small chunks (byte or word at a time).

CPU also gives:
:: memory address (physical, so the page must be tied down)
:: count

Principles of I/O Software
Issues of the software:
:: e ciency|I/O operations are very slow compared to main memory and the CPU.
Want to avoid them being a bottleneck on the system.
:: device independence|programs do not need to know about input or output device.
:: uniform naming|same naming convention regardless of the device. Large systems
typically have multiple disk drives, but user sees a common le space on top. Extend
to a distributed le system.
:: error handling|as close to device as possible, if controller detects an error it ideally
corrects it or rereads (use checksum to detect)
:: synchronous vs. asynchronous|physical I/O is asynchronous (interrupt-driven).
However want to make it appear synchronous (blocking) to the user. Can also use
polled I/O where the device driver continually polls the device (may be used by
kernel to not wait in debugging a device driver).
:: buff ering|may have to bu er data read from a device (such as a packet from
network). However, may end up and copy bu er multiple times.
:: sharable vs. dedicated| le is shared, printer cannot be shared. Operating System
must handle both kinds of devices.

I/O Software Layers
Interrupt Handlers
Bowels of the system. Occurs when a device controller wants to tell CPU something (clock
tick, write done, ready to read more, etc)
What happens on interrupt:
:: Interrupt handler gets invoked.
:: Could send a message to blocked device driver process.
:: On other systems a semaphore is signalled
Device Drivers
Contains device-dependent code. May have a device driver for a class of related devices
(terminal driver for example).
It knows details about device.
device independent request -> device driver -> device dependent request
It may queue up the request if device is already busy. Will send that request when the
current request is complete. Puts data in registers and retrieves results as needed.
Reports results to device-independent software.

Device-Independent I/O Software
Two major functions:
:: perform I/O functions common to all devices
:: provide a uniform interface to the user-level software
:: naming-read/write to terminal using /dev/tty
:: protection-look at le protection (user, group, world)
:: bu ffering-read one byte from disk. Will actually read a block of data and pass one
byte to program. .
User-Space I/O Software
For example, printf() is a library routine that calls write().
Also user-level software to support other operations. Spooling for example where a daemon
process controls access to a spooling directory. When you print, the le is put in the
directory and when your turn comes it is printed.
Also used for le transfer. UUCP networks use this approach.

Monday, 16 May 2011

Dr. Lawrence A. Farwell has invented, developed, proven, and patented the technique of Farwell Brain Fingerprinting, a new computer-based technology to identify the perpetrator of a crime accurately and scientifically by measuring brain-wave responses to crime-relevant words or pictures presented on a computer screen. Farwell Brain Fingerprinting has proven 100% accurate in over 120 tests, including tests on FBI agents, tests for a US intelligence agency and for the US Navy, and tests on real-life situations including actual crimes.

2. Brain Fingerprinting catches a serial killer

On August 5, 1999 Dr. Farwell used Brain Fingerprinting to prove that suspected serial killer James B. Grinder had raped and murdered Julie Helton 15 years earlier. Faced with an almost certain conviction and probable death sentence, Grinder pleaded guilty one week later in exchange for a sentence of life in prison without parole. He is currently serving that sentence, and has confessed to several other murders of young women.

3. Brain Fingerprinting exonerates an innocent man falsely convicted of murderOn April 25, 2000, Dr. Farwell used Brain Fingerprinting to exonerate an innocent man who has spent 22 years in prison for a murder that he did not commit. Terry Harrington was convicted in 1978 of the murder of a retired policeman who was working as a security guard, based primarily on the testimony of an alleged witness who was himself involved in the crime. Harrington was a 17-year-old black youth at the time of the crime.Brain Fingerprinting proved that Harrington's brain did not contain details of the crime that would be known to the perpetrator. Brain Fingerprinting proved not only that there was not a match between the information stored in Harrington's brain and the details of the crime, but also that there was a match between the information stored in Harrington's brain and the details of the accounts of the evening of the crime given by several alibi witnesses, who testified that Harrington was elsewhere at the time of the crime.Dr. Drew Richardson of the FBI Laboratory (phone 703-632-6704) assisted Dr. Farwell in developing the test for Harrington. Legal efforts to obtain Harrington's freedom based on Brain Fingerprinting and other newly discovered exculpatory evidence are ongoing.

4. Scientific detection of the record of the crime in the perpetrator’s brain

Farwell Brain Fingerprinting is based on the principle that the brain is central to all human acts. In a criminal act, there may or may not be many kinds of peripheral evidence, but the brain is always there, planning, executing, and recording the crime. The fundamental difference between a perpetrator and a falsely accused, innocent person is that the perpetrator, having committed the crime, has the details of the crime stored in his brain, and the innocent suspect does not. This is what Farwell Brain Fingerprinting detects scientifically.

5. Matching evidence from a crime scene with evidence on the perpetrator

Farwell Brain Fingerprinting matches evidence from a crime scene with evidence stored in the brain of the perpetrator, similarly to the way conventional fingerprinting matches fingerprints at the crime scene with the fingers of the perpetrator, and DNA fingerprinting matches biological samples from the crime scene with the DNA in the body of the perpetrator.

6. How Brain Fingerprinting works

Farwell Brain Fingerprinting works as follows. Words or pictures relevant to a crime are flashed on a computer screen, along with other, irrelevant words or pictures. Electrical brain responses are measured non-invasively through a patented headband equipped with sensors. Dr. Farwell has discovered that a specific brain-wave response called a MERMER (memory and encoding related multifaceted electroencephalographic response) is elicited when the brain processes noteworthy information it recognizes. Thus, when details of the crime that only the perpetrator would know are presented, a MERMER is emitted by the brain of a perpetrator, but not by the brain of an innocent suspect. In Farwell Brain Fingerprinting, a computer analyzes the brain response to detect the MERMER, and thus determines scientifically whether or not the specific crime-relevant information is stored in the brain of the suspect.

7. Comparison with other technologies

Conventional fingerprinting and DNA match physical evidence from a crime scene with evidence on the person of the perpetrator. Similarly, Brain Fingerprinting matches informational evidence from the crime scene with evidence stored in the brain. Fingerprints and DNA are available in only 1% of crimes. The brain is always there, planning, executing, and recording the suspect's actions.Brain Fingerprinting has nothing to do with lie detection. Rather, it is a scientific way to determine if someone has committed a specific crime or other act. No questions are asked and no answers are given during Farwell Brain Fingerprinting. As with DNA and fingerprints, the results are the same whether the person has lied or told the truth at any time.

8. Admissibility of Brain Fingerprinting in court

The admissibility of Brain Fingerprinting in court has not yet been established. The following well established features of Brain Fingerprinting, however, will be relevant when the question of admissibility is tested in court. 1) Brain Fingerprinting has been thoroughly and scientifically tested. 2) The theory and application of Brain Fingerprinting have been subject to peer review and publication. 3) The rate of error is extremely low -- virtually nonexistent -- and clear standards governing scientific techniques of operation of the technology have been established and published. 4) The theory and practice of Brain Fingerprinting have gained general acceptance in the relevant scientific community. 5) Brain Fingerprinting is non-invasive and non-testimonial.

Sunday, 15 May 2011

Brain Fingerprinting is a computer based technology invented by Dr. Lawrence A. Farwell, a neuroscientist from the USA, to measure the brain wave responses of the suspect "to crime relevant words or pictures " that would possibly link the suspect with the crime. The technique is based upon a basic premise that human brain retains all-important information for years and decades and whenever a reference is made to a particular event by means of words or pictures the brain recalls the event. The measurement of such responses by means of a suitable equipment known as EEG (Electro Encephalo Gram) which records the event related responses technically known as Event Related Potential (ERP) which is specific to a particular event for a particular person (hence known as fingerprinting) is known as Brain Fingerprinting.Fingerprinting technique works as follows. Words or pictures relevant to a crime are flashed on a computer screen, along with other, irrelevant words or pictures. Electrical brain responses are measured non-invasively through a patented headband equipped with sensors. Dr. Farwell has discovered that a specific brain-wave response called a MERMER (memory and encoding related multifaceted electroencephalographic response) is elicited when the brain processes noteworthy information it recognizes. Thus, when details of the crime that only the perpetrator would know are presented, a MERMER is emitted by the brain of a perpetrator (which is measured in terms p300, meaning 300 milliseconds emission levels). In Brain Fingerprinting, a computer analyses the brain response to detect the MERMER, and thus determines scientifically whether or not the specific crime relevant information is stored in the brain of the suspect.

In the Crime Scene Evidence Collection the BFP Expert examines the Crime Scene Evidence connected in the Crime to identify the details of the Crime that would be known only to the perpetratorThe expert then conducts the Brain Evidence Collection in order to determine whether or not the Evidence from the Crime Scene Matches Evidence Stored in the Brain of the SuspectIn the Computer Evidence Analysis the Fingerprinting system makes a mathematical determination as to whether or not this Specific Evidence is stored in the brain and computes a statistical result there upon a scientific result of either information present - the details of the crime are stored in the brain of the suspect or information absent – the details of the crime are not stored in the brain of the suspect.

III. Advantages of Brain Finger Printing.a. Identify the Crime Perpetrator quickly and scientificallyb. Record of 100 % Accuracyc. Reduced expenditure of Money and Man Hours of Law enforcementd. Provide smooth handling of suspects to the Law Enforcement Agencye. Human rights friendlyf. Likely to be an admissible evidence in Court of Law, because the evidence is scientific, objective, accurate and non-invasive in nature.

IV. Role of the I.O in Brain finger printing examinationa. Photograph the minute details of the Crime Sceneb. Photograph the Weapon ( if available ) – Very Importantc. Do not delay the decision of subjecting the suspect/accused/ witness to Brain finger Printing.d. Obtain the consent of the accused/ suspect in writing before the court of law.e. Avoid sleep-inducing medication.